Many integrated portable sensors and diagnostic systems require multiple fluid processing steps. One component of lab-on-a-chip (LOC) devices is valves, which enable control of fluid flow, isolation of different regions, and movement of sample, reagents, or reaction products without cross-contamination or unintended mixing. In recent years, the use of multilayer soft lithography for making microfabricated pneumatic valves has provided a reliable and versatile platform for advanced fluid handling in LOC devices, offering advantages of rapid prototyping and biocompatibility compared to silicon-based MEMS. Such pneumatic valves have been used for a wide range of research applications taking place in centralized facilities.
Pneumatic valves may use laboratory infrastructure such as gas tank, computers, and ground electricity for their operation. Other valves that have been developed for use in LOC applications included screw-based valves, stimuli-responsive hydrogels, passive valves, and burst valves. These valves may lack automated operation, fast response times, resistance to leakage, independence of external infrastructure, and ability to be used multiple times for an ideal portable LOC system.
Fluid handling is useful for a variety of LOC procedures. Elastomeric valves made by multilayer soft lithography, for example, have desirable features. When used with external devices such as gas tanks, computers, and ground electricity, their portability may be reduced.